A hybrid vehicle may be provided with a driveline disconnect clutch. The driveline disconnect clutch may be closed to couple an engine with an electric machine. The driveline disconnect clutch may be opened to decouple the engine from the electric machine. The engine may provide torque to the driveline when the driveline disconnect clutch is closed. The engine is stopped when the driveline disconnect clutch is open to conserve fuel. However, starting the engine and coupling the engine to the driveline may result in one or more driveline torque disturbances which may be objectionable to a driver.
The inventors herein have recognized the above-mentioned disadvantages and have developed a driveline operating method, comprising: providing positive torque to a driveline via a driveline integrated starter/generator; operating an engine at an idle speed in a speed control mode; and accelerating the engine in the speed control mode to driveline integrated starter/generator speed in response to a desired torque.
By operating an engine at an idle speed uncoupled from a driveline and accelerating the engine to a speed of the driveline, it may be possible to reduce driveline torque disturbances when driver demand torque increases. In particular, driveline torque disturbances may be reduced during an increase in driver demand torque by closing a driveline disconnect clutch that couples the engine to the driveline when engine speed and driveline speed are equivalent. Thus, the driveline integrated starter/generator may provide the driver demand torque for a short period of time, and then, engine torque can supplement driveline integrated starter/generator torque after the engine is coupled to the driveline. In this way, driveline torque response may be improved while the possibility of a driveline torque disturbance is reduced.
The present description may provide several advantages. Specifically, the approach may improve driveline torque response. Further, the approach may reduce the possibility of driveline torque disturbances.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.